Now the company, which makes public safety communications equipment, has another big investor as its partner of choice.

Motorola Solutions plans to announce on Wednesday that it has taken a $1 billion investment from the private equity firm Silver Lake.

The investment — a so-called private investment in public equity, or PIPE, in the form of debt that can be converted into common stock — is one of the biggest Silver Lake has made in its 16-year history, rivaling the $1.4 billion in cash it contributed to the management-led buyout of Dell two years ago.

In seeking out Silver Lake, a specialist in technology deals that oversees $26 billion worth of assets, Motorola Solutions is hoping to accelerate a transition from selling only radios that police officers, fire departments and other emergency workers use, to a broader emergency communications platform.

As Greg Brown, the company’s chief executive, put it in a telephone interview, the aim is to provide all the information that is “tactically useful” to workers in an emergency situation.

That means adding more complex software and other data services to Motorola Solutions’ capabilities.

Such a shift would be the latest in the company’s recent evolution. Under pressure from Mr. Icahn, the billionaire investor, the company spun off its cellphone business in 2008 and focused on government and public safety customers.

Soon after jettisoning the cellphone business, the company took on another activist, the hedge fund ValueAct Capital, which still has a representative on the board and owns a roughly 8 percent stake.

Motorola Solutions has sold off a number of other operations over the years, including a corporate network division and an enterprise services unit.

Since becoming a stand-alone operation, Motorola Solutions has grappled with ways to revive its business. Sales have stayed largely flat since 2011. The company had explored selling itself, but called off the process after finding no acceptable bids.

Mr. Brown and his team have focused in recent years both on developing a platform for government worker communications and on cutting costs. They have slashed about $550 million in operating expenses over the last three years and have laid off about 35 percent of the company’s work force since spinning off the handset business.

“The shine is really starting to show,” Mr. Brown said. “I think this is an exciting inflection point for opportunity.”

Shares of Motorola Solutions, whose market value as of Tuesday’s close was about $12.6 billion, have risen 96 percent over the last five years.

That combination of business prospects and moves toward efficiency helped draw in Silver Lake. And for Motorola Solutions, the investment firm’s specialty in technology and supporting financial maneuvers like consolidation made it a natural choice.

One of Silver Lake’s previous investments was in Avago Technologies, a chip maker that the firm helped create and then invested in further. That helped pave the way for Avago to buy a rival, Broadcom, last spring, generating a huge paper profit for the investment shop.

“What I liked in the engagement with the team at Silver Lake was their technology expertise, which I view as an accelerant and extension of our own efforts,” Mr. Brown said.

Executives from Motorola Solutions and Silver Lake began quietly negotiating several months ago, in each company’s corporate offices and sometimes in more intimate environs. One meeting took place in May at the Bay Area home of Egon Durban, a Silver Lake managing partner, where Mr. Brown and his team half-jokingly insisted that a Chicago Bulls playoff game be on the television.

As part of the deal, two top Silver Lake executives — Mr. Durban and Greg Mondre — will join Motorola Solutions’ board.

“Motorola Solutions is an iconic company and the global market leader in public safety technology,” Mr. Durban and Mr. Mondre said in a statement. “We believe it is creating a new era in data-rich public safety communications and has significant potential for growth. Its core business is unrivaled in the United States and around the world, with a broad and loyal customer base, an outstanding record of reliability and growing reach and scale driven by technology innovation.”

The transaction is expected to close on Aug. 25.

A version of this article appears in print on , on Page B2 of the New York edition with the headline: Motorola Solutions Chooses Silver Lake to Help Fund Transition Away From Radios. Order Reprints | Today’s Paper | Subscribe